The main objective of this proposal is to define more fully the individual properties of intestinal villus and crypt cells. Specifically, we wish to determine which intracellular messengers are increased in rat isolated villus and crypt enterocytes in response to agents thought to affect intestinal transport. We intend to characterize the kinetics of these interactions between the different enterocytes and agents such as vasoactive intestinal peptide (VIP), prostaglandin E1 (PGE), cholecystokinin (CCK), carbamylcholine, and serotonin. We will measure enterocyte changes in cellular cyclic AMP, cyclic GMP, and cellular calcium fluxes in response to these agents. We will evaluate the dose-response curves, time courses, temperature and pH-dependence for these agents on the villus and crypt enterocytes. We will also study the characteristics of hormone-receptor binding using radiolabeled VIP and CCK33 in these two enterocyte populations. These studies will provide a greater understanding of the relationships between maturation, function, and hormone responsiveness in both the mature villus cells and the proliferating crypt enterocytes.